[Amps] A Means of Measuring Tank Coil Inductance

[Bill Fuqua]

One easy way to get a measurement is use an oscilloscope and pulse or 
square wave generator.
Put a known capacitor  and a x10 probe across the coil. Feed the square 
wave or pulse generator in to a
loop , a coax cable to clip leads with the clip leads shorted forming a loop.
   Watch the waveform and measure the period of the damped oscillation. 
Calculate the frequency,
some scopes have a 1/t measurement, and calculate inductance. Don't forget 
to add the scopes
capacitance to that of the fixed capacitor. This will get you to 5 or 10%.

At 11:12 AM 2/2/2011 -0500, Chuck Curran wrote:
>
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>To All:
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>
>
>I have built amplifier's where I calculated the specific needs for
>inductance for the tank circuit.  I then tried several ways to measure what
>was then used in the tank coil, simply to verify the results.  I had two
>digital meters for measuring LCR components, but the ability to measure
>inductance was poor at best, when you looked at a few uH.  I then found a
>General Radio 1656 Inductance Bridge and bought it, and quickly discovered
>trying to use it at the very limits of its rated inductance range ( 1 uH )
>was something that produced less than repeatable results.  I had no
>confidence in it.
>
>
>
>Every couple of months I would search ebay in their used test equipment
>area, just to see what else was on the market.  By accident, I then found a
>circuit on-line where a fellow used a couple of IC's and a higher measuring
>frequency, and then "measured" the inductance  using a frequency counter.
>It really looked better than what I had, since it was supposed to measure
>down to .1 uH.  I was making plans to build it, however,  I then stumbled
>across an add on ebay, for a small unit, possibly similar to the circuit I
>found by Googling, but it was more advanced and provide a direct read-out in
>uH and Pf.
>
>
>
>I ordered it and also ordered a bunch of 5% axial lead inductors in the .82
>uH to 22 Uh range.  Today this little device arrived from Hong Kong.  I
>quickly plugged it in and pulled out the 5 bags of 5% inductors.  It took
>about 3-5 minutes to find the proper way of zeroing it out on inductance.  I
>then measured each of the 5% inductors.  All five inductors measured within
>5% or less of their correct value.  At the moment, I am pleasantly
>surprised!
>
>
>
>For me this is a real positive step, simply because I enjoy building so much
>and I also like to know what the actual component value is, via an actual
>measurement.  At this moment I think I can now measure inductance down to
>less than 1 uH with reasonable accuracy.
>
>
>
>The unit was $39.98 total price with shipping, and took 2 weeks exactly to
>arrive.  The component quality and construction appear to be very good.
>Lots of people seem to be selling this same unit on ebay, here is a link to
>the source I got mine from, if you have a need or interest:
>
>
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>http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem
><http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150504831155&ssPageName=
>STRK:MEWNX:IT#ht_6248wt_1139>
>&item=150504831155&ssPageName=STRK:MEWNX:IT#ht_6248wt_1139
>
>
>
>I hope this helps a few of you,
>
>
>
>Chuck  W9POU
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